.\"	$OpenBSD: EVP_EncryptInit.3,v 1.4 2016/11/26 20:26:25 schwarze Exp $
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.Dd $Mdocdate: November 26 2016 $
.Dt EVP_ENCRYPTINIT 3
.Os
.Sh NAME
.Nm EVP_CIPHER_CTX_new ,
.Nm EVP_CIPHER_CTX_init ,
.Nm EVP_CIPHER_CTX_free ,
.Nm EVP_EncryptInit_ex ,
.Nm EVP_EncryptUpdate ,
.Nm EVP_EncryptFinal_ex ,
.Nm EVP_DecryptInit_ex ,
.Nm EVP_DecryptUpdate ,
.Nm EVP_DecryptFinal_ex ,
.Nm EVP_CipherInit_ex ,
.Nm EVP_CipherUpdate ,
.Nm EVP_CipherFinal_ex ,
.Nm EVP_EncryptInit ,
.Nm EVP_EncryptFinal ,
.Nm EVP_DecryptInit ,
.Nm EVP_DecryptFinal ,
.Nm EVP_CipherInit ,
.Nm EVP_CipherFinal ,
.Nm EVP_CIPHER_CTX_set_padding ,
.Nm EVP_CIPHER_CTX_set_key_length ,
.Nm EVP_CIPHER_CTX_ctrl ,
.Nm EVP_CIPHER_CTX_cleanup ,
.Nm EVP_get_cipherbyname ,
.Nm EVP_get_cipherbynid ,
.Nm EVP_get_cipherbyobj ,
.Nm EVP_CIPHER_nid ,
.Nm EVP_CIPHER_block_size ,
.Nm EVP_CIPHER_key_length ,
.Nm EVP_CIPHER_iv_length ,
.Nm EVP_CIPHER_flags ,
.Nm EVP_CIPHER_mode ,
.Nm EVP_CIPHER_type ,
.Nm EVP_CIPHER_CTX_cipher ,
.Nm EVP_CIPHER_CTX_nid ,
.Nm EVP_CIPHER_CTX_block_size ,
.Nm EVP_CIPHER_CTX_key_length ,
.Nm EVP_CIPHER_CTX_iv_length ,
.Nm EVP_CIPHER_CTX_get_app_data ,
.Nm EVP_CIPHER_CTX_set_app_data ,
.Nm EVP_CIPHER_CTX_type ,
.Nm EVP_CIPHER_CTX_flags ,
.Nm EVP_CIPHER_CTX_mode ,
.Nm EVP_CIPHER_param_to_asn1 ,
.Nm EVP_CIPHER_asn1_to_param ,
.Nm EVP_enc_null ,
.Nm EVP_des_cbc ,
.Nm EVP_des_ecb ,
.Nm EVP_des_cfb ,
.Nm EVP_des_ofb ,
.Nm EVP_des_ede_cbc ,
.Nm EVP_des_ede ,
.Nm EVP_des_ede_ofb ,
.Nm EVP_des_ede_cfb ,
.Nm EVP_des_ede3_cbc ,
.Nm EVP_des_ede3 ,
.Nm EVP_des_ede3_ofb ,
.Nm EVP_des_ede3_cfb ,
.Nm EVP_desx_cbc ,
.Nm EVP_rc4 ,
.Nm EVP_rc4_40 ,
.Nm EVP_idea_cbc ,
.Nm EVP_idea_ecb ,
.Nm EVP_idea_cfb ,
.Nm EVP_idea_ofb ,
.Nm EVP_rc2_cbc ,
.Nm EVP_rc2_ecb ,
.Nm EVP_rc2_cfb ,
.Nm EVP_rc2_ofb ,
.Nm EVP_rc2_40_cbc ,
.Nm EVP_rc2_64_cbc ,
.Nm EVP_bf_cbc ,
.Nm EVP_bf_ecb ,
.Nm EVP_bf_cfb ,
.Nm EVP_bf_ofb ,
.Nm EVP_cast5_cbc ,
.Nm EVP_cast5_ecb ,
.Nm EVP_cast5_cfb ,
.Nm EVP_cast5_ofb ,
.Nm EVP_aes_128_cbc ,
.Nm EVP_aes_128_ecb ,
.Nm EVP_aes_128_cfb ,
.Nm EVP_aes_128_ofb ,
.Nm EVP_aes_192_cbc ,
.Nm EVP_aes_192_ecb ,
.Nm EVP_aes_192_cfb ,
.Nm EVP_aes_192_ofb ,
.Nm EVP_aes_256_cbc ,
.Nm EVP_aes_256_ecb ,
.Nm EVP_aes_256_cfb ,
.Nm EVP_aes_256_ofb ,
.Nm EVP_aes_128_gcm ,
.Nm EVP_aes_192_gcm ,
.Nm EVP_aes_256_gcm ,
.Nm EVP_aes_128_ccm ,
.Nm EVP_aes_192_ccm ,
.Nm EVP_aes_256_ccm ,
.Nm EVP_rc5_32_12_16_cbc ,
.Nm EVP_rc5_32_12_16_cfb ,
.Nm EVP_rc5_32_12_16_ecb ,
.Nm EVP_rc5_32_12_16_ofb ,
.Nm EVP_chacha20
.Nd EVP cipher routines
.Sh SYNOPSIS
.In openssl/evp.h
.Ft EVP_CIPHER_CTX *
.Fn EVP_CIPHER_CTX_new void
.Ft void
.Fo EVP_CIPHER_CTX_init
.Fa "EVP_CIPHER_CTX *ctx"
.Fc
.Ft void
.Fo EVP_CIPHER_CTX_free
.Fa "EVP_CIPHER_CTX *ctx"
.Fc
.Ft int
.Fo EVP_EncryptInit_ex
.Fa "EVP_CIPHER_CTX *ctx"
.Fa "const EVP_CIPHER *type"
.Fa "ENGINE *impl"
.Fa "unsigned char *key"
.Fa "unsigned char *iv"
.Fc
.Ft int
.Fo EVP_EncryptUpdate
.Fa "EVP_CIPHER_CTX *ctx"
.Fa "unsigned char *out"
.Fa "int *outl"
.Fa "unsigned char *in"
.Fa "int inl"
.Fc
.Ft int
.Fo EVP_EncryptFinal_ex
.Fa "EVP_CIPHER_CTX *ctx"
.Fa "unsigned char *out"
.Fa "int *outl"
.Fc
.Ft int
.Fo EVP_DecryptInit_ex
.Fa "EVP_CIPHER_CTX *ctx"
.Fa "const EVP_CIPHER *type"
.Fa "ENGINE *impl"
.Fa "unsigned char *key"
.Fa "unsigned char *iv"
.Fc
.Ft int
.Fo EVP_DecryptUpdate
.Fa "EVP_CIPHER_CTX *ctx"
.Fa "unsigned char *out"
.Fa "int *outl"
.Fa "unsigned char *in"
.Fa "int inl"
.Fc
.Ft int
.Fo EVP_DecryptFinal_ex
.Fa "EVP_CIPHER_CTX *ctx"
.Fa "unsigned char *outm"
.Fa "int *outl"
.Fc
.Ft int
.Fo EVP_CipherInit_ex
.Fa "EVP_CIPHER_CTX *ctx"
.Fa "const EVP_CIPHER *type"
.Fa "ENGINE *impl"
.Fa "unsigned char *key"
.Fa "unsigned char *iv"
.Fa "int enc"
.Fc
.Ft int
.Fo EVP_CipherUpdate
.Fa "EVP_CIPHER_CTX *ctx"
.Fa "unsigned char *out"
.Fa "int *outl"
.Fa "unsigned char *in"
.Fa "int inl"
.Fc
.Ft int
.Fo EVP_CipherFinal_ex
.Fa "EVP_CIPHER_CTX *ctx"
.Fa "unsigned char *outm"
.Fa "int *outl"
.Fc
.Ft int
.Fo EVP_EncryptInit
.Fa "EVP_CIPHER_CTX *ctx"
.Fa "const EVP_CIPHER *type"
.Fa "unsigned char *key"
.Fa "unsigned char *iv"
.Fc
.Ft int
.Fo EVP_EncryptFinal
.Fa "EVP_CIPHER_CTX *ctx"
.Fa "unsigned char *out"
.Fa "int *outl"
.Fc
.Ft int
.Fo EVP_DecryptInit
.Fa "EVP_CIPHER_CTX *ctx"
.Fa "const EVP_CIPHER *type"
.Fa "unsigned char *key"
.Fa "unsigned char *iv"
.Fc
.Ft int
.Fo EVP_DecryptFinal
.Fa "EVP_CIPHER_CTX *ctx"
.Fa "unsigned char *outm"
.Fa "int *outl"
.Fc
.Ft int
.Fo EVP_CipherInit
.Fa "EVP_CIPHER_CTX *ctx"
.Fa "const EVP_CIPHER *type"
.Fa "unsigned char *key"
.Fa "unsigned char *iv"
.Fa "int enc"
.Fc
.Ft int
.Fo EVP_CipherFinal
.Fa "EVP_CIPHER_CTX *ctx"
.Fa "unsigned char *outm"
.Fa "int *outl"
.Fc
.Ft int
.Fo EVP_CIPHER_CTX_set_padding
.Fa "EVP_CIPHER_CTX *x"
.Fa "int padding"
.Fc
.Ft int
.Fo EVP_CIPHER_CTX_set_key_length
.Fa "EVP_CIPHER_CTX *x"
.Fa "int keylen"
.Fc
.Ft int
.Fo EVP_CIPHER_CTX_ctrl
.Fa "EVP_CIPHER_CTX *ctx"
.Fa "int type"
.Fa "int arg"
.Fa "void *ptr"
.Fc
.Ft int
.Fo EVP_CIPHER_CTX_cleanup
.Fa "EVP_CIPHER_CTX *ctx"
.Fc
.Ft const EVP_CIPHER *
.Fo EVP_get_cipherbyname
.Fa "const char *name"
.Fc
.Ft const EVP_CIPHER *
.Fo EVP_get_cipherbynid
.Fa "int nid"
.Fc
.Ft const EVP_CIPHER *
.Fo EVP_get_cipherbyobj
.Fa "const ASN1_OBJECT *a"
.Fc
.Ft int
.Fo EVP_CIPHER_nid
.Fa "const EVP_CIPHER *e"
.Fc
.Ft int
.Fo EVP_CIPHER_block_size
.Fa "const EVP_CIPHER *e"
.Fc
.Ft int
.Fo EVP_CIPHER_key_length
.Fa "const EVP_CIPHER *e"
.Fc
.Ft int
.Fo EVP_CIPHER_iv_length
.Fa "const EVP_CIPHER *e"
.Fc
.Ft unsigned long
.Fo EVP_CIPHER_flags
.Fa "const EVP_CIPHER *e"
.Fc
.Ft unsigned long
.Fo EVP_CIPHER_mode
.Fa "const EVP_CIPHER *e"
.Fc
.Ft int
.Fo EVP_CIPHER_type
.Fa "const EVP_CIPHER *ctx"
.Fc
.Ft const EVP_CIPHER *
.Fo EVP_CIPHER_CTX_cipher
.Fa "const EVP_CIPHER_CTX *ctx"
.Fc
.Ft int
.Fo EVP_CIPHER_CTX_nid
.Fa "const EVP_CIPHER_CTX *ctx"
.Fc
.Ft int
.Fo EVP_CIPHER_CTX_block_size
.Fa "const EVP_CIPHER_CTX *ctx"
.Fc
.Ft int
.Fo EVP_CIPHER_CTX_key_length
.Fa "const EVP_CIPHER_CTX *ctx"
.Fc
.Ft int
.Fo EVP_CIPHER_CTX_iv_length
.Fa "const EVP_CIPHER_CTX *ctx"
.Fc
.Ft void *
.Fo EVP_CIPHER_CTX_get_app_data
.Fa "const EVP_CIPHER_CTX *ctx"
.Fc
.Ft void
.Fo EVP_CIPHER_CTX_set_app_data
.Fa "const EVP_CIPHER_CTX *ctx"
.Fa "void *data"
.Fc
.Ft int
.Fo EVP_CIPHER_CTX_type
.Fa "const EVP_CIPHER_CTX *ctx"
.Fc
.Ft unsigned long
.Fo EVP_CIPHER_CTX_flags
.Fa "const EVP_CIPHER_CTX *ctx"
.Fc
.Ft unsigned long
.Fo EVP_CIPHER_CTX_mode
.Fa "const EVP_CIPHER_CTX *ctx"
.Fc
.Ft int
.Fo EVP_CIPHER_param_to_asn1
.Fa "EVP_CIPHER_CTX *c"
.Fa "ASN1_TYPE *type"
.Fc
.Ft int
.Fo EVP_CIPHER_asn1_to_param
.Fa "EVP_CIPHER_CTX *c"
.Fa "ASN1_TYPE *type"
.Fc
.Sh DESCRIPTION
The EVP cipher routines are a high level interface to certain symmetric
ciphers.
.Pp
.Fn EVP_CIPHER_CTX_new
creates a cipher context.
.Pp
.Fn EVP_CIPHER_CTX_init
initializes the cipher context
.Fa ctx .
.Pp
.Fn EVP_CIPHER_CTX_free
clears all information from a cipher context and frees up any
allocated memory associate with it, including
.Fa ctx
itself.
This function should be called after all operations using a cipher
are complete, so sensitive information does not remain in memory.
If
.Fa ctx
is a
.Dv NULL
pointer, no action occurs.
.Pp
.Fn EVP_EncryptInit_ex
sets up the cipher context
.Fa ctx
for encryption with cipher
.Fa type
from
.Vt ENGINE
.Fa impl .
.Fa ctx
must be initialized before calling this function.
.Fa type
is normally supplied by a function such as
.Fn EVP_aes_256_cbc .
If
.Fa impl
is
.Dv NULL ,
then the default implementation is used.
.Fa key
is the symmetric key to use and
.Fa iv
is the IV to use (if necessary).
The actual number of bytes used for the
key and IV depends on the cipher.
It is possible to set all parameters to
.Dv NULL
except
.Fa type
in an initial call and supply the remaining parameters in subsequent
calls, all of which have
.Fa type
set to
.Dv NULL .
This is done when the default cipher parameters are not appropriate.
.Pp
.Fn EVP_EncryptUpdate
encrypts
.Fa inl
bytes from the buffer
.Fa in
and writes the encrypted version to
.Fa out .
This function can be called multiple times to encrypt successive blocks
of data.
The amount of data written depends on the block alignment of the
encrypted data: as a result the amount of data written may be anything
from zero bytes to (inl + cipher_block_size - 1) so
.Fa out
should contain sufficient room.
The actual number of bytes written is placed in
.Fa outl .
.Pp
If padding is enabled (the default) then
.Fn EVP_EncryptFinal_ex
encrypts the "final" data, that is any data that remains in a partial
block.
It uses NOTES (aka PKCS padding).
The encrypted final data is written to
.Fa out
which should have sufficient space for one cipher block.
The number of bytes written is placed in
.Fa outl .
After this function is called the encryption operation is finished and
no further calls to
.Fn EVP_EncryptUpdate
should be made.
.Pp
If padding is disabled then
.Fn EVP_EncryptFinal_ex
will not encrypt any more data and it will return an error if any data
remains in a partial block: that is if the total data length is not a
multiple of the block size.
.Pp
.Fn EVP_DecryptInit_ex ,
.Fn EVP_DecryptUpdate ,
and
.Fn EVP_DecryptFinal_ex
are the corresponding decryption operations.
.Fn EVP_DecryptFinal
will return an error code if padding is enabled and the final block is
not correctly formatted.
The parameters and restrictions are identical to the encryption
operations except that if padding is enabled the decrypted data buffer
.Fa out
passed to
.Fn EVP_DecryptUpdate
should have sufficient room for (inl + cipher_block_size) bytes
unless the cipher block size is 1 in which case
.Fa inl
bytes is sufficient.
.Pp
.Fn EVP_CipherInit_ex ,
.Fn EVP_CipherUpdate ,
and
.Fn EVP_CipherFinal_ex
are functions that can be used for decryption or encryption.
The operation performed depends on the value of the
.Fa enc
parameter.
It should be set to 1 for encryption, 0 for decryption and -1 to leave
the value unchanged (the actual value of
.Fa enc
being supplied in a previous call).
.Pp
.Fn EVP_CIPHER_CTX_cleanup
clears all information from a cipher context and free up any allocated
memory associated with it.
It should be called after all operations using a cipher are complete so
sensitive information does not remain in memory.
.Pp
.Fn EVP_EncryptInit ,
.Fn EVP_DecryptInit ,
and
.Fn EVP_CipherInit
behave in a similar way to
.Fn EVP_EncryptInit_ex ,
.Fn EVP_DecryptInit_ex ,
and
.Fn EVP_CipherInit_ex
except the
.Fa ctx
parameter does not need to be initialized and they always use the
default cipher implementation.
.Pp
.Fn EVP_EncryptFinal ,
.Fn EVP_DecryptFinal ,
and
.Fn EVP_CipherFinal
are identical to
.Fn EVP_EncryptFinal_ex ,
.Fn EVP_DecryptFinal_ex ,
and
.Fn EVP_CipherFinal_ex .
In previous releases of OpenSSL, they also used to clean up the
.Fa ctx ,
but this is no longer done and
.Fn EVP_CIPHER_CTX_cleanup
must be called to free any context resources.
.Pp
.Fn EVP_get_cipherbyname ,
.Fn EVP_get_cipherbynid ,
and
.Fn EVP_get_cipherbyobj
return an
.Vt EVP_CIPHER
structure when passed a cipher name, a NID or an
.Vt ASN1_OBJECT
structure.
.Pp
.Fn EVP_CIPHER_nid
and
.Fn EVP_CIPHER_CTX_nid
return the NID of a cipher when passed an
.Vt EVP_CIPHER
or
.Vt EVP_CIPHER_CTX
structure.
The actual NID value is an internal value which may not have a
corresponding OBJECT IDENTIFIER.
.Pp
.Fn EVP_CIPHER_CTX_set_padding
enables or disables padding.
This function should be called after the context is set up for
encryption or decryption with
.Fn EVP_EncryptInit_ex ,
.Fn EVP_DecryptInit_ex ,
or
EVP_CipherInit_ex .
By default encryption operations are padded using standard block padding
and the padding is checked and removed when decrypting.
If the
.Fa padding
parameter is zero, then no padding is performed, the total amount of data
encrypted or decrypted must then be a multiple of the block size or an
error will occur.
.Pp
.Fn EVP_CIPHER_key_length
and
.Fn EVP_CIPHER_CTX_key_length
return the key length of a cipher when passed an
.Vt EVP_CIPHER
or
.Vt EVP_CIPHER_CTX
structure.
The constant
.Dv EVP_MAX_KEY_LENGTH
is the maximum key length for all ciphers.
Note: although
.Fn EVP_CIPHER_key_length
is fixed for a given cipher, the value of
.Fn EVP_CIPHER_CTX_key_length
may be different for variable key length ciphers.
.Pp
.Fn EVP_CIPHER_CTX_set_key_length
sets the key length of the cipher ctx.
If the cipher is a fixed length cipher, then attempting to set the key
length to any value other than the fixed value is an error.
.Pp
.Fn EVP_CIPHER_iv_length
and
.Fn EVP_CIPHER_CTX_iv_length
return the IV length of a cipher when passed an
.Vt EVP_CIPHER
or
.Vt EVP_CIPHER_CTX .
It will return zero if the cipher does not use an IV.
The constant
.Dv EVP_MAX_IV_LENGTH
is the maximum IV length for all ciphers.
.Pp
.Fn EVP_CIPHER_block_size
and
.Fn EVP_CIPHER_CTX_block_size
return the block size of a cipher when passed an
.Vt EVP_CIPHER
or
.Vt EVP_CIPHER_CTX
structure.
The constant
.Dv EVP_MAX_BLOCK_LENGTH
is also the maximum block length for all ciphers.
.Pp
.Fn EVP_CIPHER_type
and
.Fn EVP_CIPHER_CTX_type
return the type of the passed cipher or context.
This "type" is the actual NID of the cipher OBJECT IDENTIFIER as such it
ignores the cipher parameters and 40-bit RC2 and 128-bit RC2 have the
same NID.
If the cipher does not have an object identifier or does not
have ASN.1 support this function will return
.Dv NID_undef .
.Pp
.Fn EVP_CIPHER_CTX_cipher
returns the
.Vt EVP_CIPHER
structure when passed an
.Vt EVP_CIPHER_CTX
structure.
.Pp
.Fn EVP_CIPHER_mode
and
.Fn EVP_CIPHER_CTX_mode
return the block cipher mode:
.Dv EVP_CIPH_ECB_MODE ,
.Dv EVP_CIPH_CBC_MODE ,
.Dv EVP_CIPH_CFB_MODE ,
or
.Dv EVP_CIPH_OFB_MODE .
If the cipher is a stream cipher then
.Dv EVP_CIPH_STREAM_CIPHER
is returned.
.Pp
.Fn EVP_CIPHER_param_to_asn1
sets the ASN.1
.Vt AlgorithmIdentifier
parameter based on the passed cipher.
This will typically include any parameters and an IV.
The cipher IV (if any) must be set when this call is made.
This call should be made before the cipher is actually "used" (before any
.Fn EVP_EncryptUpdate
or
.Fn EVP_DecryptUpdate
calls, for example).
This function may fail if the cipher does not have any ASN.1 support.
.Pp
.Fn EVP_CIPHER_asn1_to_param
sets the cipher parameters based on an ASN.1
.Vt AlgorithmIdentifier
parameter.
The precise effect depends on the cipher.
In the case of RC2, for example, it will set the IV and effective
key length.
This function should be called after the base cipher type is set but
before the key is set.
For example
.Fn EVP_CipherInit
will be called with the IV and key set to
.Dv NULL ,
.Fn EVP_CIPHER_asn1_to_param
will be called and finally
.Fn EVP_CipherInit
again with all parameters except the key set to
.Dv NULL .
It is possible for this function to fail if the cipher does not
have any ASN.1 support or the parameters cannot be set (for example
the RC2 effective key length is not supported).
.Pp
.Fn EVP_CIPHER_CTX_ctrl
allows various cipher specific parameters to be determined and set.
Currently only the RC2 effective key length and the number of rounds of
RC5 can be set.
.Pp
Where possible the EVP interface to symmetric ciphers should be
used in preference to the low level interfaces.
This is because the code then becomes transparent to the cipher used and
much more flexible.
.Pp
PKCS padding works by adding n padding bytes of value n to make the
total length of the encrypted data a multiple of the block size.
Padding is always added so if the data is already a multiple of the
block size n will equal the block size.
For example if the block size is 8 and 11 bytes are to be encrypted then
5 padding bytes of value 5 will be added.
.Pp
When decrypting the final block is checked to see if it has the correct
form.
.Pp
Although the decryption operation can produce an error if padding is
enabled, it is not a strong test that the input data or key is correct.
A random block has better than 1 in 256 chance of being of the correct
format and problems with the input data earlier on will not produce a
final decrypt error.
.Pp
If padding is disabled then the decryption operation will always succeed
if the total amount of data decrypted is a multiple of the block size.
.Pp
The functions
.Fn EVP_EncryptInit ,
.Fn EVP_EncryptFinal ,
.Fn EVP_DecryptInit ,
.Fn EVP_CipherInit ,
and
.Fn EVP_CipherFinal
are obsolete but are retained for compatibility with existing code.
New code should use
.Fn EVP_EncryptInit_ex ,
.Fn EVP_EncryptFinal_ex ,
.Fn EVP_DecryptInit_ex ,
.Fn EVP_DecryptFinal_ex ,
.Fn EVP_CipherInit_ex ,
and
.Fn EVP_CipherFinal_ex
because they can reuse an existing context without allocating and
freeing it up on each call.
.Pp
.Fn EVP_get_cipherbynid
and
.Fn EVP_get_cipherbyobj
are implemented as macros.
.Sh RETURN VALUES
.Fn EVP_CIPHER_CTX_new
returns a pointer to a newly created
.Vt EVP_CIPHER_CTX
for success or
.Dv NULL
for failure.
.Pp
.Fn EVP_EncryptInit_ex ,
.Fn EVP_EncryptUpdate ,
and
.Fn EVP_EncryptFinal_ex
return 1 for success and 0 for failure.
.Pp
.Fn EVP_DecryptInit_ex
and
.Fn EVP_DecryptUpdate
return 1 for success and 0 for failure.
.Fn EVP_DecryptFinal_ex
returns 0 if the decrypt failed or 1 for success.
.Pp
.Fn EVP_CipherInit_ex
and
.Fn EVP_CipherUpdate
return 1 for success and 0 for failure.
.Fn EVP_CipherFinal_ex
returns 0 for a decryption failure or 1 for success.
.Pp
.Fn EVP_CIPHER_CTX_cleanup
returns 1 for success and 0 for failure.
.Pp
.Fn EVP_get_cipherbyname ,
.Fn EVP_get_cipherbynid ,
and
.Fn EVP_get_cipherbyobj
return an
.Vt EVP_CIPHER
structure or
.Dv NULL
on error.
.Pp
.Fn EVP_CIPHER_nid
and
.Fn EVP_CIPHER_CTX_nid
return a NID.
.Pp
.Fn EVP_CIPHER_block_size
and
.Fn EVP_CIPHER_CTX_block_size
return the block size.
.Pp
.Fn EVP_CIPHER_key_length
and
.Fn EVP_CIPHER_CTX_key_length
return the key length.
.Pp
.Fn EVP_CIPHER_CTX_set_padding
always returns 1.
.Pp
.Fn EVP_CIPHER_iv_length
and
.Fn EVP_CIPHER_CTX_iv_length
return the IV length or zero if the cipher does not use an IV.
.Pp
.Fn EVP_CIPHER_type
and
.Fn EVP_CIPHER_CTX_type
return the NID of the cipher's OBJECT IDENTIFIER or
.Dv NID_undef
if it has no defined OBJECT IDENTIFIER.
.Pp
.Fn EVP_CIPHER_CTX_cipher
returns an
.Vt EVP_CIPHER
structure.
.Pp
.Fn EVP_CIPHER_param_to_asn1
and
.Fn EVP_CIPHER_asn1_to_param
return greater than zero for success and zero or a negative number
for failure.
.Sh CIPHER LISTING
All algorithms have a fixed key length unless otherwise stated.
.Bl -tag -width Ds
.It Fn EVP_enc_null
Null cipher: does nothing.
.It Xo
.Fn EVP_aes_128_cbc ,
.Fn EVP_aes_128_ecb ,
.Fn EVP_aes_128_cfb ,
.Fn EVP_aes_128_ofb
.Xc
AES with a 128-bit key in CBC, ECB, CFB and OFB modes respectively.
.It Xo
.Fn EVP_aes_192_cbc ,
.Fn EVP_aes_192_ecb ,
.Fn EVP_aes_192_cfb ,
.Fn EVP_aes_192_ofb
.Xc
AES with a 192-bit key in CBC, ECB, CFB and OFB modes respectively.
.It Xo
.Fn EVP_aes_256_cbc ,
.Fn EVP_aes_256_ecb ,
.Fn EVP_aes_256_cfb ,
.Fn EVP_aes_256_ofb
.Xc
AES with a 256-bit key in CBC, ECB, CFB and OFB modes respectively.
.It Xo
.Fn EVP_des_cbc ,
.Fn EVP_des_ecb ,
.Fn EVP_des_cfb ,
.Fn EVP_des_ofb
.Xc
DES in CBC, ECB, CFB and OFB modes respectively.
.It Xo
.Fn EVP_des_ede_cbc ,
.Fn EVP_des_ede ,
.Fn EVP_des_ede_ofb ,
.Fn EVP_des_ede_cfb
.Xc
Two key triple DES in CBC, ECB, CFB and OFB modes respectively.
.It Xo
.Fn EVP_des_ede3_cbc ,
.Fn EVP_des_ede3 ,
.Fn EVP_des_ede3_ofb ,
.Fn EVP_des_ede3_cfb
.Xc
Three key triple DES in CBC, ECB, CFB and OFB modes respectively.
.It Fn EVP_desx_cbc
DESX algorithm in CBC mode.
.It Fn EVP_rc4
RC4 stream cipher.
This is a variable key length cipher with default key length 128 bits.
.It Fn EVP_rc4_40
RC4 stream cipher with 40-bit key length.
This is obsolete and new code should use
.Fn EVP_rc4
and the
.Fn EVP_CIPHER_CTX_set_key_length
function.
.It Xo
.Fn EVP_idea_cbc ,
.Fn EVP_idea_ecb ,
.Fn EVP_idea_cfb ,
.Fn EVP_idea_ofb
.Xc
IDEA encryption algorithm in CBC, ECB, CFB and OFB modes respectively.
.It Xo
.Fn EVP_rc2_cbc ,
.Fn EVP_rc2_ecb ,
.Fn EVP_rc2_cfb ,
.Fn EVP_rc2_ofb
.Xc
RC2 encryption algorithm in CBC, ECB, CFB and OFB modes respectively.
This is a variable key length cipher with an additional parameter called
"effective key bits" or "effective key length".
By default both are set to 128 bits.
.It Xo
.Fn EVP_rc2_40_cbc ,
.Fn EVP_rc2_64_cbc
.Xc
RC2 algorithm in CBC mode with a default key length and effective key
length of 40 and 64 bits.
These are obsolete and new code should use
.Fn EVP_rc2_cbc ,
.Fn EVP_CIPHER_CTX_set_key_length ,
and
.Fn EVP_CIPHER_CTX_ctrl
to set the key length and effective key length.
.It Xo
.Fn EVP_bf_cbc ,
.Fn EVP_bf_ecb ,
.Fn EVP_bf_cfb ,
.Fn EVP_bf_ofb
.Xc
Blowfish encryption algorithm in CBC, ECB, CFB and OFB modes
respectively.
This is a variable key length cipher.
.It Xo
.Fn EVP_cast5_cbc ,
.Fn EVP_cast5_ecb ,
.Fn EVP_cast5_cfb ,
.Fn EVP_cast5_ofb
.Xc
CAST encryption algorithm in CBC, ECB, CFB and OFB modes respectively.
This is a variable key length cipher.
.It Xo
.Fn EVP_rc5_32_12_16_cbc ,
.Fn EVP_rc5_32_12_16_ecb ,
.Fn EVP_rc5_32_12_16_cfb ,
.Fn EVP_rc5_32_12_16_ofb
.Xc
RC5 encryption algorithm in CBC, ECB, CFB and OFB modes respectively.
This is a variable key length cipher with an additional "number of
rounds" parameter.
By default the key length is set to 128 bits and 12 rounds.
.It Xo
.Fn EVP_aes_128_gcm ,
.Fn EVP_aes_192_gcm ,
.Fn EVP_aes_256_gcm
.Xc
AES Galois Counter Mode (GCM) for 128, 192 and 256 bit keys respectively.
These ciphers require additional control operations to function
correctly: see the GCM mode section below for details.
.It Xo
.Fn EVP_aes_128_ccm ,
.Fn EVP_aes_192_ccm ,
.Fn EVP_aes_256_ccm
.Xc
AES Counter with CBC-MAC Mode (CCM) for 128, 192 and 256 bit keys
respectively.
These ciphers require additional control operations to function
correctly: see CCM mode section below for details.
.It Fn EVP_chacha20
The ChaCha20 stream cipher.
The key length is 256 bits, the IV is 96 bits long.
.El
.Ss GCM mode
For GCM mode ciphers, the behaviour of the EVP interface
is subtly altered and several additional ctrl operations are
supported.
.Pp
To specify any additional authenticated data (AAD), a call to
.Fn EVP_CipherUpdate ,
.Fn EVP_EncryptUpdate ,
or
.Fn EVP_DecryptUpdate
should be made with the output parameter out set to
.Dv NULL .
.Pp
When decrypting, the return value of
.Fn EVP_DecryptFinal
or
.Fn EVP_CipherFinal
indicates if the operation was successful.
If it does not indicate success, the authentication operation has
failed and any output data MUST NOT be used as it is corrupted.
.Pp
The following ctrls are supported in GCM mode:
.Bl -tag -width Ds
.It Fn EVP_CIPHER_CTX_ctrl ctx EVP_CTRL_GCM_SET_IVLEN ivlen NULL
Sets the IV length: this call can only be made before specifying an IV.
If not called, a default IV length is used.
For GCM AES the default is 12, i.e. 96 bits.
.It Fn EVP_CIPHER_CTX_ctrl ctx EVP_CTRL_GCM_GET_TAG taglen tag
Writes
.Fa taglen
bytes of the tag value to the buffer indicated by
.Fa tag .
This call can only be made when encrypting data and after all data has
been processed, e.g. after an
.Fn EVP_EncryptFinal
call.
.It Fn EVP_CIPHER_CTX_ctrl ctx EVP_CTRL_GCM_SET_TAG taglen tag
Sets the expected tag to
.Fa taglen
bytes from
.Fa tag .
This call is only legal when decrypting data and must be made before
any data is processed, e.g. before any
.Fa EVP_DecryptUpdate
call.
.El
.Ss CCM mode
The behaviour of CCM mode ciphers is similar to GCM mode, but with
a few additional requirements and different ctrl values.
.Pp
Like GCM mode any additional authenticated data (AAD) is passed
by calling
.Fn EVP_CipherUpdate ,
.Fn EVP_EncryptUpdate ,
or
.Fn EVP_DecryptUpdate
with the output parameter out set to
.Dv NULL .
Additionally, the total
plaintext or ciphertext length MUST be passed to
.Fn EVP_CipherUpdate ,
.Fn EVP_EncryptUpdate ,
or
.Fn EVP_DecryptUpdate
with the output and input
parameters
.Pq Fa in No and Fa out
set to
.Dv NULL
and the length passed in the
.Fa inl
parameter.
.Pp
The following ctrls are supported in CCM mode:
.Bl -tag -width Ds
.It Fn EVP_CIPHER_CTX_ctrl ctx EVP_CTRL_CCM_SET_TAG taglen tag
This call is made to set the expected CCM tag value when decrypting or
the length of the tag (with the
.Fa tag
parameter set to
.Dv NULL )
when encrypting.
The tag length is often referred to as M.
If not set, a default value is used (12 for AES).
.It Fn EVP_CIPHER_CTX_ctrl ctx EVP_CTRL_CCM_SET_L ivlen NULL
Sets the CCM L value.
If not set, a default is used (8 for AES).
.It Fn EVP_CIPHER_CTX_ctrl ctx EVP_CTRL_CCM_SET_IVLEN ivlen NULL
Sets the CCM nonce (IV) length: this call can only be made before
specifying an nonce value.
The nonce length is given by 15 - L so it is 7 by default for AES.
.El
.Sh EXAMPLES
Encrypt a string using blowfish:
.Bd -literal -offset 3n
int
do_crypt(char *outfile)
{
	unsigned char outbuf[1024];
	int outlen, tmplen;
	/*
	 * Bogus key and IV: we'd normally set these from
	 * another source.
	 */
	unsigned char key[] = {0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15};
	unsigned char iv[] = {1,2,3,4,5,6,7,8};
	const char intext[] = "Some Crypto Text";
	EVP_CIPHER_CTX ctx;
	FILE *out;
	EVP_CIPHER_CTX_init(&ctx);
	EVP_EncryptInit_ex(&ctx, EVP_bf_cbc(), NULL, key, iv);

	if (!EVP_EncryptUpdate(&ctx, outbuf, &outlen, intext,
	    strlen(intext))) {
		/* Error */
		return 0;
	}
	/*
	 * Buffer passed to EVP_EncryptFinal() must be after data just
	 * encrypted to avoid overwriting it.
	 */
	if (!EVP_EncryptFinal_ex(&ctx, outbuf + outlen, &tmplen)) {
		/* Error */
		return 0;
	}
	outlen += tmplen;
	EVP_CIPHER_CTX_cleanup(&ctx);
	/*
	 * Need binary mode for fopen because encrypted data is
	 * binary data. Also cannot use strlen() on it because
	 * it won't be NUL terminated and may contain embedded
	 * NULs.
	 */
	out = fopen(outfile, "wb");
	fwrite(outbuf, 1, outlen, out);
	fclose(out);
	return 1;
}
.Ed
.Pp
The ciphertext from the above example can be decrypted using the
.Xr openssl 1
utility with the command line:
.Bd -literal -offset indent
openssl bf -in cipher.bin -K 000102030405060708090A0B0C0D0E0F \e
           -iv 0102030405060708 -d
.Ed
.Pp
General encryption, decryption function example using FILE I/O and RC2
with an 80-bit key:
.Bd -literal
int
do_crypt(FILE *in, FILE *out, int do_encrypt)
{
	/* Allow enough space in output buffer for additional block */
	inbuf[1024], outbuf[1024 + EVP_MAX_BLOCK_LENGTH];
	int inlen, outlen;
	/*
	 * Bogus key and IV: we'd normally set these from
	 * another source.
	 */
	unsigned char key[] = "0123456789";
	unsigned char iv[] = "12345678";

	/* Don't set key or IV because we will modify the parameters */
	EVP_CIPHER_CTX_init(&ctx);
	EVP_CipherInit_ex(&ctx, EVP_rc2(), NULL, NULL, NULL, do_encrypt);
	EVP_CIPHER_CTX_set_key_length(&ctx, 10);
	/* We finished modifying parameters so now we can set key and IV */
	EVP_CipherInit_ex(&ctx, NULL, NULL, key, iv, do_encrypt);

	for(;;) {
		inlen = fread(inbuf, 1, 1024, in);
		if (inlen <= 0)
			break;
		if (!EVP_CipherUpdate(&ctx, outbuf, &outlen, inbuf,
		    inlen)) {
			/* Error */
			EVP_CIPHER_CTX_cleanup(&ctx);
			return 0;
		}
		fwrite(outbuf, 1, outlen, out);
	}
	if (!EVP_CipherFinal_ex(&ctx, outbuf, &outlen)) {
		/* Error */
		EVP_CIPHER_CTX_cleanup(&ctx);
		return 0;
	}
	fwrite(outbuf, 1, outlen, out);

	EVP_CIPHER_CTX_cleanup(&ctx);
	return 1;
}
.Ed
.Sh SEE ALSO
.Xr evp 3
.Sh HISTORY
.Fn EVP_CIPHER_CTX_init ,
.Fn EVP_EncryptInit_ex ,
.Fn EVP_EncryptFinal_ex ,
.Fn EVP_DecryptInit_ex ,
.Fn EVP_DecryptFinal_ex ,
.Fn EVP_CipherInit_ex ,
.Fn EVP_CipherFinal_ex ,
and
.Fn EVP_CIPHER_CTX_set_padding
appeared in OpenSSL 0.9.7.
.Sh BUGS
For RC5 the number of rounds can currently only be set to 8, 12 or 16.
This is a limitation of the current RC5 code rather than the EVP
interface.
.Pp
.Dv EVP_MAX_KEY_LENGTH
and
.Dv EVP_MAX_IV_LENGTH
only refer to the internal ciphers with default key lengths.
If custom ciphers exceed these values the results are unpredictable.
This is because it has become standard practice to define a generic key
as a fixed unsigned char array containing
.Dv EVP_MAX_KEY_LENGTH
bytes.
.Pp
The ASN.1 code is incomplete (and sometimes inaccurate).
It has only been tested for certain common S/MIME ciphers
(RC2, DES, triple DES) in CBC mode.
